Well it started out to be a good day

I got the new tank I have been saving for for a few months yesterday! I am a happy man! Well for a day anyway.



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Then it all turned to %$#^^%$&*& as you can see. My new Yong Heng has been sounding kind of funny lately and since I overheated it so bad it was smoking shortly after I got it. I pulled out the old one that I had overheated three times over 100deg Celsius but it never smoked and have been using it as of late. I began filling the nice big tank 15min at a time then a half hour resting to let it cool down. All went well till I hit about 3500psi and then I blew a breaker twice so I got out the newer unit and thought it did not sound too bad now for some reason. Filled the tank to almost 4Kpsi and then it let loose with this horrible noise. I shut it down immediately and almost as fast tore it apart thinking I had done major damage. I fought with the stainless lines though they were really tight but finally prevailed. You can see the problem is just the second stage upper piston that easily screws on and off. It will take me longer to find parts than to fix the thing. I expect the older unit needs something similar but I can probly baby it along for a bit till I get the new one back in service. Grr..



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I tore it down way further than I needed to make the repair just to troubleshoot the problem.

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The top part of the piston just above the bottom ring screws off and was only finger tight. If I can find a replacement I will be in good shape. Otherwise a whole piston and cylinder kit complete with all of the lines is only $58.

GRRR...

But at least these parts are readily available and also inexpensive. They are fairly easy to werq on too.






 
I use Ice in my water bucket, more ice than water. I also bought a Ryobi wet tile saw water pump to replace the one that came with my Y/H as the original was not dependable. I run mine for 20 to 40 minutes depending on how low I run my air bottle (106 cu/ft) down before topping it off. One other thing I noticed the bolts holding the hi pressure (top) portion of the machine vibrated loose and it started to make a different noise. Fortunately I noticed and shut it down , snugged them up and its still running about 2 years now. 
 
I overheated both of mine because I did not plug the pump in. My Bad evil me. I use a half gallon jug full of ice in my two gallon pail to cool things and it will run for twenty minutes or so before it gets hot. Since I don't run it longer than that I am good. I did recently purchase an outlet strip that will handle the load so now when I turn on the power the pump starts up before I start the compressor. Wish I had done that a year or two ago. Such a deal.
 
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You should get any carbon buildup off your pistons and anywhere else you see it while it’s torn down.

https://www.homemodelenginemachinist.com/threads/4500psi-air-compressor.18948/

I’ve wanted to share this entire thread with everyone who is operating ANY HPA compressor and or cylinders. The article explains a lot. I have a 205 gph Fluval German aquarium pump I would have run on a Yong Heng if I had went that way. If you read everything you’ll see too cold is as bad or worse than too hot. I figured lots of room temp water. Without instrumentation or heat reading gun it’s probably like trying to tune perfectly with no chronograph.

I worked on PET blow mold wheels in York so I found this interesting on many levels. 
 
+++ what airgunfans says. Using large jugs of frozen water does not work nearly as good as a bag or two of ice. You need the surface area that loose ice gives for cooling. Next time take your large tank to a shop for the deep fill then only use your pump to top off from about 3000 to 4500. Those little pumps last a lot longer that way. Sorry for all your troubles Mike. I have some spare parts if you run into trouble but no pistons. Nick
 
It might be a bit late but this is probably all you need. https://www.aliexpress.com/item/32863290524.html?spm=a2g0o.detail.1000060.1.60146176k3gLpo&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.146401.0&scm_id=1007.13339.146401.0&scm-url=1007.13339.146401.0&pvid=532ab712-97bd-4bc7-a1da-c5a171e1d954 or for slightly more $ https://www.aliexpress.com/item/32952512274.html?spm=a2g0o.detail.1000060.1.343d6065BMtlBU&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.146401.0&scm_id=1007.13339.146401.0&scm-url=1007.13339.146401.0&pvid=54849258-7720-4357-bea7-1124205113a0 + maybe gaskets. I know that I'm going to get flack for this but all the piston failure of this type that I've seen has been from people using ice for coolant and comments are suggesting ways to decrease the temperature even more. The damage does appear to be caused by heat and fatigue but I think that I'll be sticking to plain water in mine.
 
The damage does appear to be caused by heat and fatigue .

In this case the OP stated that the piston head got loose. As the result, the piston head stuck out more and hit the cylinder head. The Yong Heng people has also told me that it's a common reason so the use of thread locker is essential.

OK, I missed that point. Got it now. I'll stick by my theory that adding ice is not a good idea.
 
It might be a bit late but this is probably all you need. https://www.aliexpress.com/item/32863290524.html?spm=a2g0o.detail.1000060.1.60146176k3gLpo&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.146401.0&scm_id=1007.13339.146401.0&scm-url=1007.13339.146401.0&pvid=532ab712-97bd-4bc7-a1da-c5a171e1d954 or for slightly more $ https://www.aliexpress.com/item/32952512274.html?spm=a2g0o.detail.1000060.1.343d6065BMtlBU&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.146401.0&scm_id=1007.13339.146401.0&scm-url=1007.13339.146401.0&pvid=54849258-7720-4357-bea7-1124205113a0 + maybe gaskets. I know that I'm going to get flack for this but all the piston failure of this type that I've seen has been from people using ice for coolant and comments are suggesting ways to decrease the temperature even more. The damage does appear to be caused by heat and fatigue but I think that I'll be sticking to plain water in mine.


That's the exact one I got and a couple gaskets cuz it looked like they were about to give out.
 
Two things : 

1) Get a new 2nd stage piston + ring. Make sure that it's a new version which is stronger. see https://www.airgunnation.com/topic/yong-heng-second-stage-piston-breaking-not-any-more/

2) Make sure that you apply Loctite to the threads of the piston. I use Loctite 272, a high-temperature, high-strength type

Then it should be good to go again.


Not sure f I got the new or old version of piston cuz it has the rings already on it. It was also the only one I saw when searching. I got some Permatex sleeve retainer it's good to 400 degrees should werq. Bought it awhile back for some reason but never even opened it yet. Wish they had put some thread locker on at the factory. The threads were shiny clean when I unscrewed the piston.
 
Wish they had put some thread locker on at the factory. The threads were shiny clean when I unscrewed the piston.

On My Yong Heng, they have definitely put thread lockers on all the threads on the 2nd-stage piston because I had to use quite some force before I could unscrew them. The threads were shiny but there were fragments of cured thread lockers dropping out.